I cannot find any mention of the mapsurfer box in either AQ or LbNA. Is it a premium member's only box?

The last couple of times I went to Mackinac Islands have been after Labor Day. In October, most shops and hotels were closed and it was cold. In September, the shops and hotels were open, the weather was cool, and there were few people. No crowds. No families. I didn't have to worry about muggles. I was able to letterbox to my heart's content. When letterboxing in the summer, though, muggles were a big problem.

But the island is still somewhat expensive, even in the shoulder season.